Adolescent depression is a highly prevalent condition that is associated with multiple impairments (Fergusson & Woodward, 2002). This has led to an interest in developing programs for the prevention and early intervention of depression, particularly programs that can be delivered in schools where children and adolescents are most likely to receive services (President's New Freedom Commission on Mental Health, 2003). Based on the need for innovative prevention programs for depression and the advantages of delivering such an intervention in schools, we developed a school-based group indicated preventive intervention, Interpersonal Psychotherapy-Adolescent Skills Training (IPT-AST; Young & Mufson, 2003). In two small-scale randomized controlled trials, IPT-AST has been markedly efficacious immediately post-intervention and the effects are sustained at six month follow-up (Young, Mufson, & Davies, 2006a; Young, Mufson, & Gallop, 2009). The next logical step is to conduct a large-scale efficacy study comparing IPT-AST to a more rigorous control condition and to examine mediators and moderators of IPT-AST outcomes. The proposed study is a randomized controlled trial comparing IPT-AST to group counseling (GC) for the prevention of depression in adolescents. The project will: (1) identify adolescents with elevated depressive symptoms but who do not meet criteria for a current mood disorder diagnosis; (2) randomize eligible adolescents to either IPT-AST (N = 100) or GC (N = 100); (3) assess depressive symptoms, depressive disorders, global functioning, interpersonal functioning, comorbid conditions and school related indices at baseline, mid-intervention, post-intervention, and at 6-, 12-, 18-, and 24-month follow-up; (4) examine the effects of IPT-AST on depression and various domains of functioning at each time point; and (5) conduct analyses to examine potential mediators and moderators of the association between IPT-AST and depression outcomes. This study will yield data on the efficacy of IPT-AST relative to GC for the prevention of depressive symptoms and depressive disorders. It will also provide information about the mechanisms of action of IPT-AST and determine for whom IPT-AST is most effective.